Curable compositions

ABSTRACT

A curable composition is provided, comprising a monofunctional (meth)arcylate monomer, a poly functional (meth)acrylate monomer, a (meth)acrylate monomer containing an acidic group and at least one (meth)acryloyloxyl group in its molecule, a monofunctional (meth)acrylamide monomer, and a trialkylboron and/or a partial oxide thereof. The composition has improved low-temperature curability at approximately room temperature and water-resistant adherence, and excellent adhesiveness to tooth substances including enamel and dentin and dental alloys, and gives no adverse influence of stimulation to dental pulp. Most preferably, the composition is used as a bonding agent for dental composite resins.

TECHNICAL FIELD

This invention relates to an acrylate composition. More particularly, itrelates to a curable composition useful for dental bonding agents(adhesives) and the like, which has improved low-temperature curabilityat room temperature and water-resistant adherence, excellentadhesiveness to tooth substances such as enamel and dentin and dentalalloys, and no adverse influence including stimulation for dental pulp.

BACKGROUND ART

A number of bonding agents have been proposed for orthodontic andrestorative treatments which typical are catalyzed compositionscomprises a radical-polymerizable monomer such as a (meth)acrylate vinylmonomer. For example, Japanese Patent Application Kokai No. 60-44508proposes a curable composition comprising an acrylate or methacrylatevinyl monomer, an aromatic carboxylic acid or an anhydride thereofcontaining an acryloyloxyl or methacryloyloxyl group, an amine, and asulfinic acid or a salt thereof. Japanese Patent Application Kokai No.53-39331 discloses a bonding agent comprising an acrylate ormethacrylate ester which is liquid at room temperature, an amine, asulfinic acid or a salt thereof, and a peroxide. Nihon Shika Hoken(Japanese Dental and Hygienic Journal), 28, 270 (1985) reports a bondingagent comprising methyl methacrylate, 4-META, and tributylboran (TBB).

However, conventional adhesives and curable compositions have problemsthat they have to be treated by etchants such as phosphoric acid andcitric acid in order to obtain improved adherence to dental substances,and that it is difficult to obtain sufficient adherence to dentinparticularly if an etching treatment is not carried out to dentin atall, and that an opening in dentin tube is caused by the etchingtreatment resulting in stimulation to dental pulp.

Therefore, the above-mentioned problems can be solved by the presentinvention. An object of the present invention is to provide a curablecomposition having improved curability at room temperature andwater-resistant adherence. Another object of the present invention is toprovide a curable composition having improved adherence to toothsubstances such as enamel and dentin and dental alloys, particularlydentin. A further object of the present invention is to provide acurable composition which can be used as a dental adhesive to bondcomposite resins for tooth restoration without any adverse influenceincluding stimulation of dental pulp.

DISCLOSURE OF THE INVENTION

According to the present invention, there is provided a curablecomposition comprising (A) a monofunctional (meth)acrylate monomer, (B)a polyfunctional (meth)acrylate monomer, (C) a (meth)acrylate monomercontaining an acidic group and at least one acryloyloxyl ormethacryloyloxyl group in its molecule, (D) a monofunctional(meth)acrylamide monomer of the general formula (I): ##STR1## wherein Ris H or CH₃, and (E) a trialkylboron and/or a partial oxide thereof.

The present invention is hereinafter discribed in detail.

The monofunctional (meth)acrylate monomer (A) used in the curablecomposition of the present invention may contain in its molecule afunctional group other than an acidic group. Examples of themonofunctional (meth)acrylate monomer include (meth)acrylates containinga hydrocarbon group such as methyl (meth)acrylate, ethyl (meth)acrylate,butyl (meth)acrylate, hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate,dddecyl (meth)acrylate, lauryl (meth)acrylate, cyclohexyl(meth)acrylate, benzyl (meth)acrylate, and isobornyl (meth)acrylate;(meth)acrylates containing a hydroxyl group such as 2-hydroxyethyl(meth)acrylate and 2-hydroxypropyl (meth)acrylate; (meth)acrylatescontaining an ethylene glycol unit such as ethylene glycol monomethylether (meth)acrylate, ethylene glycol monoethyl ether (meth)acrylate,ethylene glycol monododecyl ether (meth)acrylate, diethylene glycolmonomethyl ether (meth)crylate, polyethylene glycol monomethyl ether(meth)acrylate, and polyethylene glycol monoethyl ether (meth)acrylate;(meth)acrylates containing a fluorine-substituted group such astrifluoroethyl (meth)acrylate, and perfluorooctyl (meth)acrylate; silane(meth)acrylates such as γ-(meth)acryloyloxypropyltrimethoxysilane, andγ-(meth)acryloyloxypropyltri(trimethylsiloxy)silane; andtetrahydrofurfuryl (meth)acrylate. They may be used alone or inadmixture of two or more.

Preferred are alkyl (meth)acrylates such as methyl acrylate andmethacrylate, ethyl (meth)acrylate, hexyl (meth)acrylate, and dodecyl(meth)acrylate, and hydroxylcontaining (meth)acrylates such as2-hydroxyethyl (meth)acrylate, and 2-hydroxypropyl (meth)acrylate. Mostpreferably, methyl methacrylate, n-hexyl methacrylate, 2-hydroxyethylmethacrylate and 2-hydroxypropyl methacrylate monomers and a mixturethereof are used.

Examples of the polyfunctional acrylate or methacrylate monomer (B) usedin the curable composition include poly(meth)acrylates of alkane polyolssuch as ethylene glycol di(meth)acrylate, propylene glycoldi(meth)acrylate, butylene glycol di(meth)acrylate, neopentyl glycoldi(meth)acrylate, hexylene glycol di(meth)acrylate, trimethylolpropanetri(meth)acrylate, glycerin tri(meth)acrylate, and pentaerythritoltetra(meth)acrylate; and poly(meth)acrylates of (poly)oxyalkane polyolssuch as diethylene glycol di(meth)acrylate, dipropylene glycoldi(meth)acrylate, triethylene glycol di(meth)acrylate, tetraethyleneglycol di(meth)acrylate, dibutylene glycol di(meth)acrylate, anddipentaerythritol hexa(meth)acrylate; epoxy (meth)acrylates of thegeneral formula (II): ##STR2## wherein R is H or CH₃,

n is 0 or a positive integer, and

R¹ is --(CH₂)₂ --, --(CH₂)₄ --, ##STR3## cycloaliphatic or aromaticdi(meth)acrylates of the general formula (III): wherein R is H or CH₃,and ##STR4## cycloaliphatic di(meth)acrylates of the general formula(IV): ##STR5## wherein R is H or CH₃, and ##STR6##

polyfunctional acrylates and methacrylates containing at least oneurethane bond in their molecule. An example of the polyfunctional(meth)acrylates is an adduct of 1 mol of diisocyanate and 2 mol of ahydroxy groupcontaining (meth)acrylates such as 2-hydroxyethyl(meth)acrylates.

The diisocyanates may be used aliphatic, cycloaliphatic or aromaticdiisocyanate. Examples of the diisocyanates include hexamethylenediisocyanate, lysindiisocyanate,2,2(4),4-trimethylhexamethylenediisocyanate,dicyclohexyldimethylmethane-P,P'-diisocyanate, isophorondiisocyanate,trilendiisocyanate, xylilenediisocyanate, diphenylmethanediisocyanate,and naphthalenediisocyanate. Further examples of the diisocyanateinclude ##STR7## wherein R is H or CH₃, ##STR8## wherein R is H or CH₃,##STR9## wherein R is H or CH₃, ##STR10## wherein R is H or CH₃,##STR11## wherein R is H or CH₃, ##STR12## wherein R is H or CH₃,##STR13## wherein R is H or CH₃, ##STR14## wherein R is H or CH₃, and##STR15## wherein R is H or CH₃.

Other examples of monomers (B) include the polyfunctional(meth)acrylates of the general formula (V): ##STR16## wherein R is H orCH₃, R⁴ is a divalent aromatic residue which has at least one aromaticring and may have an oxygen or sulfur atom in tis molecule, and n and mare positive integers. Examples of the polyfunctional (meth)acrylates ofthe general formula (V) include ##STR17## wherein R is H or CH₃, andm+n=2 to 20, ##STR18## wherein R is H or CH₃, and m+n=2 to 20, ##STR19##wherein R is H or CH₃, and m+n=2 to 20, ##STR20## wherein R is H or CH₃,and m+n=2 to 20, ##STR21## wherein R is H or CH₃, and m+n=2 to 20,##STR22## wherein R is H or CH₃, and m+n=2 to 20.

Among these polyfunctional (meth)acrylate monomers, preferred are themonomers of alkane polyol poly(methacrylate. (poly)oxyalkanepolyolpoly(meth)acrylate, epoxy(meth)acrylate, aliphatic or cycloaliphatic(meth)acrylate containing at least one urethane bond in its molecule,and (poly)oxyalkanepolyol poly(meth)acrylate having aromatic rings. Mostpreferred monomers are ethyleneglycol di(meth)acrylate, neopentylglycol(meth)acrylate, diethyleneglycol di(meth)acrylate, triethylene glycoldi(meth)acrylate, ##STR23## wherein R is H or CH₃, ##STR24## wherein Ris H or CH₃, ##STR25## wherein R is H or CH₃, ##STR26## wherein R is Hor CH₃, and m+n=2 to 10, and ##STR27## wherein R is H or CH₃, and m+n=2to 10.

They may be used alone or in admixture of two or more.

In the curable composition according to the present invention, the(meth)acrylate monomer containing an acidic group and at least one(meth)acryloyloxyl group in its molecule (C) includes (C₁) aromaticpolycarboxylic acids having at leaqst one (meth)acryloyloxyl group permolecule or anhydrides thereof and (C₂) partial esters of phosphoric orsulfonic acid having at least one (meth)acyloyloxyl group per molecule,such as monoesters and diesters of phosphoric acid and mixtures thereof,and monoesters of sulfonic acid.

Examples of the aromatic polycarboxylic acid having at least one(meth)acryloyloxyl group per molecure (C₁) are(meth)acryloyloxyl-containing aromatic polycarboxylic acids oranhydrides thereof having the structure wherein an alkane polyol has atleast two hydroxyl groups per molecule and may contain an oxygen atom,at least one of its hydroxyl groups forms an ester with (meth)acrylicacid and at least one of its hydroxyl groups forms an ester with onecarboxyl group of an aromatic polycarboxylic acid having at least threecarboxyl groups.

The preferred aromatic polycarboxylic acids containing at least threecarboxyl groups are aromatic polycarboxylic acids in which at least twoof the carboxyl groups are attached to the adjoining carbon atom on thearomatic nucleus. Examples of the aromatic polycarboxylic acids arehemimellitic acid, trimellitic acid, prehnitic acid, mellophanic acid,and pyromellitic acid.

The (meth)acryloyloxyl-containing aromatic polycarboxylic acids oranhydrides thereof include 4-(meth)acryloyloxymethoxycarbonylphthalicacid or an anhydride thereof, 4-(meth)acryloyloxyethoxy-carbonylphthalicacid or an anhydride thereof, 4-(meth)acryloyloxybutoxycarbonylphthalicacid or an anhydride thereof, ##STR28## wherein R is H or CH₃, and n isan integer of from 6 to 12, ##STR29## wherein R is H or CH₃, and n is aninteger of from 2 to 50, ##STR30## wherein R is H or CH₃, and n is aninteger of from 1 to 50,

4-[2-hydroxy-3-(meth)acryloyoxypropoxycarbonyl]phthalic acid or an acidanhydride thereof, 2,3-bis(3,4-dicarboxybenzoyloxy)propylmethacrylate2,3-bis(3,4-dicarboxybenzoyloxy)propylmethacrylate or an acid anhydridethereof, and 2-(3,4-dicarboxylbenzoyloxy)-1,3-dimethacryloyoxypropane oran acid anhydride thereof.

The partial esters of phosphoric or sulfonic acid having at least one(meth)acryloyloxyl group per molecule (C₂) include monoesters anddiesters of sulfonic acid, for example, 2-(meth)acryloyloxyehtylphenylacid phosphate, bis-[2-(meth)acryloyl-oxyethyl]acid phosphate,bis[3-(meth)acryloxypropyl]acid phosphate,2-(meth)acryloyloxyethylphenyl phosphonate, ##STR31##

Among these (meth)acrylate monomers containing an acidic group and atleast one (meth)acryloyloxyl group in its molecule (C), preferred arearomatic polycarboxylic acids having at least one (meth)acryloyloxylgroup per molecule or acid anhydrides thereof (C₁). More preferred are4-(meth)acryloyloxy-ethoxycarbonylphthalic acid or its acid anhydride.Most preferably, 4-(meth)acryloyloxyethoxycarbonylphthalic acidanhydride is used because of improved adherence to tooth andwater-durability.

In the curable composition of the present invention, a monofunctional(meth)acrylate monomer (D) of the general formula (I) is used. Examplesof the monofunctional (meth)acrylamide monomer are3-(meth)acryloylaminosalicylic acid, 4-(meth)acryloyl-aminosalicylicacid, 5-(meth)acryloylaminosalicylic acid,3-hydroxy-2-(meth)acryloylaminobenzoic acid,3-hydroxy-4-(meth)acryloylaminobenzoic acid,3-hydroxy-5-(meth)acryloylaminobenzoic acid,3-hydroxy-6-(meth)acryloylaminobenzoic acid,4-hydroxy-2-(meth)acrylaminobenzoic acid, and4-hydroxy-3-(meth)acryloylaminobenzoic acid. They may be used alone orin admixture of two or more. Among these monofunctional (meth)acrylatemonomer, preferred are 3-(meth)acryloylaminosalicylic acid,4-(meth)acryloylaminosalicylic acid, and 5-(meth)acryloylaminosalicylicacid. Most preferably, 4-(meth)acryloylaminosalicylic acid and5-(meth)acryloylaminosalicylic acid are used alone or in admixture.

The curable composition of the present invention further comprises (E) atrialkylboron or its partial oxide. Examples of the trialkylboroninclude triethylboron, tripropylboron, triisopropylboron,tri-n-butylboron, tri-n-amylboron, triisoamylboron, tri-sec-amylboron,and partial oxides of these trialkylborons in which the trialkylboronsare partially oxidized. Preferably, tri-n-butylboron and its partialoxides are used.

In the curable composition of the present invention, the proportion ofthe monofunctional (meth)acrylate monomer (A) and the polyfunctional(meth)acrylate monomer (B) blended therein is not particularly limited.Better results are obtained when the curable composition generallycontains 5 to 95% by weight of the monofunctional (meth)acrylate monomer(A) and 95 to 5% by weight of the polyfunctional (meth)acrylate monomer(B), preferably 10 to 95% by weight of the monofunctional (meth)acrylatemonomer (A) and 90 to 5% by weight of the polyfunctional (meth)acrylatemonomer (B), and most preferably 25 to 90% by weight of themonofunctional (meth)acrylate monomer (A) and 75 to 10% by weight of thepolyfunctional (meth)acrylate monomer (B), because adhesiveness todentin and water-durability exhibit improved, particularly adhesivenessand water-durability to non-etched dentin.

In the curable composition of the present invention, the proportion ofthe acidic group-containing (meth)acrylate monomer (C) blended thereingenerally ranges from 1 to 50 parts by weight, preferably from 3 to 30parts by weight, most preferably from 5 to 15 parts by weight per 100parts by weight of the total of the monofunctional (meth)acrylatemonomer (A) and the polyfunctional (meth)acrylate monomer (B) blendedtherein.

In the curable composition of the present invention, the proportion ofthe monofunctional (meth)acrylamide monomer (D) of the general formula(I) blended therein generally ranges from 0.1 to 50 parts by weight,preferably from 0.3 to 30 parts by weight, most preferably from 1 to 15parts by weight per 100 parts by weight of the total of themonofunctional (meth)acrylate monomer (A) and the polyfunctional(meth)acrylate monomer (B) blended therein.

In the curable composition of the present invention, the proportion ofthe trialkylboron or its partial oxide (E) blended therein generallyranges from 2 to 100 parts by weight, preferably from 5 to 70 parts byweight, most preferably from 5 to 50 parts by weight per 100 parts byweight of the total of the monofunctional (meth)acrylate monomer (A),the polyfunctional (meth)acrylate monomer (B), the acidicgroup-containing (meth)acrylate monomer (C) and the monofunctional(meth)acrylamide monomer (D) of the general formula (I) blended therein.

The curable composition of the present invention may contain any desiredadditives in addition to the abovementioned essential components, forexample, other polymerizable monomers, organic solvents, powderinorganic fillers, organic polymers, and polymerization retarders.

Examples of the other polymerizable monomers include vinyl halogenidessuch as vinyl chloride and vinyl bromide; vinyl esters such as vinylacetate and vinyl propyonate; vinyl ethers such as methylvinyl ether,ethylvinyl ether and isobutylvinyl ether; alkenyl benzenes such asstyrene, vinyltoluene, α-methylstyrene, chloromethylstyrene andstilbene.

Examples of the organic solvents include ethyl alcohol, acetone, ethylacetate, diethyl ether, tetrahydrofuran, N,N-dimethyl acetoamide,N-methyl pyrorydone and dimethyl sulfoxide.

Examples of the powder inorganic fillers include kaolin, talc, clay,calcium carbonate, silica, silicaalumina, titanium oxide, calciumphosphate, ground glass, and ground quartz.

Examples of the organic polymers include wax, ethylene-vinyl acetatecopolymers, and polymethylacrylate, polymetylmethacrylate, andcopolymers thereof. These fillers or additives may be blended in anydesired proportion.

The curable composition of the present invention is prepared by mixingeach of the above-mentioned components (A), (B), (C), (D) and (E), andmay also contain other optional components. In this case, the proportionof each of the above-mentioned components (A), (B), (C), (D) and (E) maybe adjusted as desired. In order to get good procedure at the use, apart of them is dissolved in an organic solvent, mixed the solution withthe other components and applied it to dental surface before curingleading to polymerized-curing the compositions, or each of thecomponents is separately applied to the surface leading topolymerized-curing the compositions. Since the trialkylboron or itspartial oxide (E) starts polymerization reaction with the (meth)acrylatemonomers (A), (B) and (C) and the (meth)acrylamide monomer (D) withinseveral seconds to several ten minutes after their mixing, thetrialkylboron (E) is kept separate from the above-mentioned components(A), (B), (C) and (D) and mixed with the latter components immediatelybefore use.

BEST MODE FOR CARRYING OUT THE INVENTION

Examples of the present invention are presented below by way ofillustration and not by way of limitation.

Evaluation of the curable composition of the present invention isdescribed below together with examples of preparing the photo-curablecomposite resin used in Examples and Comparative Examples. Theabbreviations used herein have the following meanings.

MMA: methyl methacrylate,

HMA: n-hexyl methacrylate,

HEMA: 2-hydroxyethyl methacrylate,

HEPA: 2-hydroxypropyl methacrylate,

DPEMA: ##STR32##

2.6E: ##STR33##

RDMA: ##STR34##

UDMA: ##STR35##

4-META: ##STR36##

4-MET: ##STR37##

4-MASA: ##STR38##

5-MASA: ##STR39##

TBB-0: partial oxide of tri-n-butylboron

BPO: benzoyl peroxide

DEPT: diethanol p-toluidine

PTSNa: sodium p-toluenesulfonate

HQME: hydroquinone monomethylether

1. Evaluation of adhesiveness

The enamel or dentin surface of a bovine anterior tooth on its labialface was fully polished with #600 emery paper to smoothen the surface.The enamel was etched for 30 seconds with an aqueous solution of 65% byweight of phosphoric acid. After thorough rinsing, the etched surfacewas dried by air blowing. A piece of adhesive tape of about 13 mm by 13mm having a circular opening of 5 mm in diameter was attached to theetched surface. The bonding agent described in Examples or ComparativeExamples was applied to the surface in the opening, and lightly airblown. A cylindrical mold of polytetrafluoroethylene having a diameterof 5 mm and a height of 2 mm was mated with the circular opening in theadhesive tape and filled with the photo-polymerizable composite resindescribed later. The composite resin filling was covered on the surfacewith a cellophane sheet, and exposed for 30 seconds to visible lightfrom a visible light source, Translux (manufactured by Kulzer) to curethe composite resin. An acryl resin bar was bonded to the surface of thecured composite resin with an adhesive, Super-Bond C&B (manufactured bySun Medical K.K.) to form a bond test specimen. The specimen was allowedto stand for 30 minutes at room temperature, immersed for 24 hours inwater at a temperature of 37° C., allowed to stand for 10 minutes in airat a temperature of 23° C., and then subjected to a tensile test at atemperature of 23° C. and a pulling rate of 2 mm/min to measure abonding force. After the bond test, the rupture surface exhibited bovinetooth rupture, cohesive rupture of the composite resin, or interfacialrupture between the composite resin and the dentin.

2. Preparation of photo-curable composite resin

A composition was prepared by milling 7.5 grams of triethylene glycoldimethacrylate, 7.5 grams of 1,3-bis -(methacryloxyethoxy)benzene, 15grams of an adduct of 1 mol of 2,2,4-trimethylhexamethylenediaminediisocyanate and 2 mol of 2-hydroxyethyl methacrylate, 40 grams of acomposite filler synthesized by the following method, 30 grams of finelydivided silica (RM-50, Nihon Aerosil K.K.), and 4 mg of hydroquinonemonomethyl ether in a two-roll mill at 35° C. A photo-curable compositeresin was prepared by combining 10 grams of the composition with 45 mgof camphorquinone and 45 mg of 4-diethylaminobenzoic acid and fullyadmixing the mixture with a spatula.

3. Preparation of composite filler

A solution of 0.1 gram benzoyl peroxide in 10 grams oftrimethylolpropane trimethacrylate was placed in an agate mortar. Finelydivided silica (Aerosil R972, Nihon Aerosil K.K., average particle sizeof 16 mμ) was added to the solution in increments while mixing. Assilica was added, the viscosity of the mixture gradually increased. Whenthe mixture became somewhat crumby, it was transferred to a small-sizerubber roll mill. Finely divided silica was further added until a totalamount of 9.5 grams was reached. The resulting paste was removed fromthe mill and het cured for 10 minutes in a press at a mold temperatureof 110° C. under a pressure of 150 to 200 kg/cm². The cured product wasground in a ball mill so as to pass a 230 mesh screen, obtaining 18.0grams of a composite filler. The filler had an average particle size of11 μm.

EXAMPLE 1

A monomer mixed liquid (A) was prepared by mixing 6.0 grams of methylmethacrylate (MMA), 3.0 grams of 1,3-bis(methacryloxy)benzene (RDMA),1.0 gram of 4-methacryoxy ethoxy carboxylic phthalic acid anhydride(4-META), 0.1 gram of 4-methacryloyl aminosalicylic acid (4-MASA), and2.0 milligrams of hydroquinone monomethyl ether (HQME) at roomtemperature. A curable composition was prepared by mixing 2 parts byweight of the monomer liquid (A) with 1 part by weight of a partialoxide of tri-n-butylboron (TBB-0, Sun Medical K.K.). The composition wasapplied to the tooth surface with a small brush. A bond test specimenwas then prepared by the aforesaid method. The results are shown inTable 1.

EXAMPLES 2-11 AND COMPARATIVE EXAMPLES 1-4

Bond test specimens were prepared by repeating the procedure of Example1 except that the monomers used in Example 1 were replaced by othermonomers shown in Table 1 in the amounts reported in Table 1. Theresults are shown in Table 1.

COMPARATIVE EXAMPLE 5

A monomer liquid (A) was prepared by mixing 3.0 grams of MMA, 3.0 gramsof HEMA, 3.0 grams of 2,6E, 1.0 gram of 4-HETA, 0.2 grams of 5-MASA, 0.1gram of BPO and 2.0 milligrams of HQME at room temperature. Separately,a liquid (B) was prepared by dissolving 0.05 grams of DEPT and 0.2 gramsof PTSNa in 9.75 grams of 99% ethyl alcohol. The curable composition wasprepared by mixing equal parts by weigh of (A) and (B) at roomtemperature. The composition was applied to the tooth surface with asmall brush. A bond test specimen was prepared by the aforesaid method.The results are shown in Table.

                                      TABLE 1                                     __________________________________________________________________________                           Example 1                                                                           Example 2                                                                           Example 3                                                                           Example 4                                                                           Example 5                                                                             Example                __________________________________________________________________________                                                           6                      Curable composition                                                           Monofunctional (meth)acrylate monomer (A)                                     type                   MMA   MMA   MMA   MMA   MMA/HEMA                                                                              MMA/HEMA               amount, weight ratio   --    --    --    --    90/10   50/50                  Polyfunctional (meth)acrylate monomer (B)                                     type                   RDMA  2.6E  DPEMA UDMA  DPEMA   UDMA                   amount, B/(A + B) wt % 33    33    33    33    33      33                     Acidic group-containing (meth)acrylate                                        monomer (C)                                                                   type                   4-META                                                                              4-MET 4-META                                                                              4-MET 4-META  4-META                 amount, C/(A + B) wt % 11    11    11    11    11      11                     Monofunctional (meth)acrylamide monomer (D)                                   type                   4-MASA                                                                              4-MASA                                                                              5-MASA                                                                              5-MASA                                                                              4-MASA  4-MASA                 amount, D/(A + B) wt % 1.1   1.1   1.1   1.1   2.2     5.5                    Partial oxide of trialkylboron (E)                                            type                   TBB.O TBB.O TBB.O TBB.O TBB.O   TBB.O                  amount, E/(A + B + C + D) wt %                                                                       50    50    50    50    50      50                     Adhesiveness                                                                  Enamel, after water immersion                                                                        197   215   190   193   205     193                    @ 37° C., 1 day, kg/cm.sup.2                                           Dentin, after water immersion                                                                        68    63    82    77    70      67                     @ 37° C., 1 day, kg/cm.sup.2                                           __________________________________________________________________________                               Example 7                                                                             Example 8                                                                             Example 9                                                                           Example                                                                             Example                __________________________________________________________________________                                                           11                     Curable composition                                                           Monofunctional (meth)acrylate monomer (A)                                     type                       MMA/HEMA                                                                              MMA/HEMA                                                                              HEMA  HMA   MMA/HEMA               amount, weight ratio       80/20   50/50   --    --    20/80                  Polyfunctional (meth)acrylate monomer (B)                                     type                       2.6E    RDMA    2.6E  2.6E  2.6E                   amount, B/(A + B) wt %     33      33      50    50    50                     Acidic group-containing (meth)acrylate monomer (C)                            type                       4-META  4-META  4-META                                                                              4-META                                                                              4-MET                  amount, C/(A + B) wt %     11      11      10    10    10                     Monofunctional (meth)acrylamide monomer (D)                                   type                       5-MASA  5-MASA  4-MASA                                                                              5-MASA                                                                              5-MASA                 amount, D/(A + B) wt %     2.2     5.5     5     1     3                      Partial oxide of trialkylboron (E)                                            type                       TBB.O   TBB.O   TBB.O TBB.O TBB.O                  amount, E/(A + B + C + D) wt %                                                                           50      50      50    33    25                     Adhesiveness                                                                  Enamel, after water immersion                                                                            220     211     178   195   182                    @ 37° C., 1 day, kg/cm.sup.2                                           Dentin, after water immersion                                                                            93      83      71    90    90                     @ 37° C., 1 day, kg/cm.sup.2                                           __________________________________________________________________________                          Comparative                                                                          Comparative                                                                          Comparative                                                                           Comparative                                                                           Comparative                                     Example 1                                                                            Example 2                                                                            Example 3                                                                             Example 4                                                                             Example                   __________________________________________________________________________                                                        5                         Curable composition                                                           Monofunctional (meth)acrylate monomer (A)                                     type                  --     MMA    MMA/HEMA                                                                              MMA/HEMA                                                                              MMA/HEMA                  amount, weight ratio  --     --     80/20   80/20   50/50                     Polyfunctional (meth)acrylate monomer (B)                                     type                  2.6E   --     2.6E    2.6E    2.6E                      amount, B/(A + B) wt %                                                                              100    0      33      33      33                        Acidic group-containing (meth)acrylate                                        monomer (C)                                                                   type                  4-META 4-META --      4-META  4-META                    amount, C/(A + B) wt %                                                                              11     11     0       11      11                        Monofunctional (meth)acrylaide monomer (D)                                    type                  5-MASA 5-MASA 5-MASA  --      5-MASA                    amount, D/(A + B) wt %                                                                              1.1    1.1    2       0       2.2                       Partial oxide of trialkylboron (E)                                            type                  TBB.O  TBB.O  TBB.O   TBB.O   (BPO/DEPT/PTSNa)          amount, E/(A + B + C + D) wt %                                                                      50     50     50      50      1/0.5/2                   Adhesiveness                                                                  Enamel, after water immersion                                                                       131    175    103     215     135                       @ 37° C., 1 day, kg/cm.sup.2                                           Dentin, after water immersion                                                                       27     23     27      33      12                        @ 37° C., 1 day, kg/cm.sup.2                                           __________________________________________________________________________

EXAMPLE 12

A solution (a), dissolving 1.0 gram of 4-methacryloylaminosalicylic acid(4-MASA) in 19 grams of ethyl alcohol was applied to the tooth surface.The ethyl alcohol was almost evaporated by lightly air blowing.Separately, a monomer liquid was prepared by mixing 6.0 grams of methylmethacrylate (MMA), 3.0 grams of 1,3-bis(methacryloxy ethoxy) benzene(RDMA), 1.0 gram of 4-methacryloxy ethoxy carboxylic phthalic acidanhydride (4-META) and 2.0 milligrams of hydroquinone monomethyl ether(HQME) at room temperature. A liquid (b) was prepared by mixing 2 partsby weight of the monomer liquid with 1 part by weight of a partial oxideof tri-n-butylboron (TBB-0, Sun Medical K.K.). The liquid (b) of theequal amount of the solution (a) was applied to the tooth surface. Abond test specimen was prepared by the aforesaid method. The results areshown in Table 2.

EXAMPLES 13-17

Bond test specimens were prepared by repeating the procedure of Example12 except that the monomers used in Example 12 were replaced by othermonomers shown in Table 2 in the amounts shown in Table 2. The resultsare shown in Table 2.

                                      TABLE 2                                     __________________________________________________________________________                          Com-                                                                          parative                                                                            Comparative                                                                          Comparative                                                                          Comparative                                                                          Comparative                                                                          Comparative                                 Example 12                                                                          Example 13                                                                           Example 14                                                                           Example 15                                                                           Example                                                                              Example               __________________________________________________________________________                                                            17                    Curable composition                                                           Monofunctional (meth)acrylate monomer (A)                                     type                  MMA   MMA/   MMA/   MMA/   MMA/   MMA                                               HEMA   HEMA   HEMA   HEMA                         amount, weight ratio  --    85/15  50/50  85/15  85/15  --                    Polyfunctional (meth)acrylate monomer (B)                                     type                  RDMA  2.6E   DPEMA  2.6E   UDMA   RDMA                  amount, B/(A + B) wt %                                                                              33    33     33     33     50     30                    Acidic group-containing (meth)acrylate                                        monomer (C)                                                                   type                  4-META                                                                              4-META 4-MET  4-META 4-META 4-META                amount, C/(A + B) wt %                                                                              11    11     11     11     10     5                     Monofunctional (meth)acrylamide monomer (D)                                   type                  4-MASA                                                                              5-MASA 5-MASA 5-MASA 4-MASA 4-MASA                amount, D/(A + B) wt %                                                                              5.5   5.5    5.5    1.1    5      5                     Partial oxide of trialkylboron (E)                                            type                  TBB.O TBB.O  TBB.O  TBB.O  TBB.O  TBB.O                 amount, E/(A + B + C + D) wt %                                                                      50    50     50     50     25     50                    Adhesiveness                                                                  Enamel, after water immersion                                                                       213   210    185    203    218    177                   @  37° C., 1 day, kg/cm.sup.2                                          Dentin, after water immersion                                                                       80    125    97     118    107    79                    @ 37° C., 1 day, kg/cm.sup.2                                           __________________________________________________________________________

The bond tests showed that the compositions of the Examples had superiorwater-resistant adherence to enamel and dentin, on the contrary, thecompositions of the Comparative Examples which lack at least one of thecomponents (A), (B), (C), (D) and (E) of the present invention hadinferior water-resistant adherence to enamel and/or dentin.

INDUSTRIAL APPLICABILITY

The composition of the present invention comprises the above-mentioned(A), (B), (C), (D) and (E). The composition has improved low-temperaturecurability at room temperature and water-resistant adherence, andexhibits excellent adhesiveness to tooth substances including enamel anddentin and dental alloys, and gives no adverse influence includingstimulation of dental pulp.

Therefore, the composition can be used as a bonding agent not only fordental composite resins and rigid resins, but also for various compositeresins used in precision working other than dental applications. Mostpreferably, the composition is used as a bonding agent for dentalcomposite resins.

We claim:
 1. A curable composition comprising,(A) a monofunctional(meth)acrylate monomer, (B) a polyfunctional (meth)acrylate monomer, (C)a (meth)acrylate monomer containing an acidic group and at least one(meth)acryloyloxyl group in its molecule, (D) a monofunctional(meth)acrylamide monomer of the general formula (I): ##STR40## wherein Ris H or CH₃, and (E) a trialkylboron and/or a partial oxide thereof. 2.The curable composition of claim 1 wherein (A) comprises 5 to 95% byweight and (B) comprises 95 to 5% by weight based on the total weight of(A) and (B), (C) comprises 1 to 50 parts by weight per 100 parts byweight of the total of (A) and (B), (D) comprises 0.1 to 50 parts byweight per 100 parts by weight of the total of (A) and (B), and (E)comprises 2 to 100 parts by weight per 100 parts by weight of the totalof (A), (B), (C) and (D).